Conventionally various speakers (for example, Patent Document 1) are mounted on a vehicle as a moving object. The speaker disclosed in Patent Document 1 includes: a cylindrical frame having a base plate; a vibrating unit received in the frame; and a magnetic circuit unit attached to the frame, and generating sound by vibrating the vibrating unit.
The frame of the speaker has a substantially cylindrical shape for attaching to a door of a vehicle. An attaching part having a specific opening is formed on the door to which the speaker is attached. It is difficult to freely change the size of the opening. Further, a receiving part for attaching the frame to the attaching part is formed on the frame. An inner diameter of the receiving part is substantially the same as an outer diameter of the attaching part.
Incidentally, if a projection projected outward is formed on a side wall of the frame, and an outer diameter of the projection is larger than the inner diameter of the receiving part, when the speaker is inserted into the attaching part, the attaching part contacts the projection so that the speaker cannot be attached to the door. Accordingly, an outer diameter of the frame of the speaker is formed in a substantially cylindrical shape such that the outer diameter is reduced as the receiving part extends from an inner periphery to a bottom.
The vibrating unit is received in the frame. The vibrating unit includes: a voice coil to which voice currents are supplied; a drive cone attached to the voice coil; a diaphragm; and two edge units. The center axes of the drive cone and the diaphragm are aligned (hereafter referred to as coaxial), and an outer diameter of the diaphragm is formed large. The diaphragm is arranged on a sound emission side relative to the drive cone.
For a purpose that the outer diameters of the diaphragm and the drive cone are substantially the same, the projection projected outward may be formed on the side wall of the frame, and the outer periphery of the drive cone may be attached to the projection. However, as above described, because there is a problem that the projection contacts the attaching part, the outer diameter of the diaphragm is formed larger than that of the drive cone.
Each of the two edge units is made of resin, and has an annular section. One of the two edge units is attached to an outer periphery of the diaphragm and the frame, and the other edge unit is attached to an outer periphery of the drive cone and the frame. The edge units allow the drive cone and the diaphragm to move in a vibration direction of the voice coil.
Further, a sectional shape of the one edge unit is formed in an arc shape projecting toward a sound emission direction, and a sectional shape of the other edge unit is formed in an arc shape projecting in a reverse direction of the sound emission direction. Further, because the outer diameter of the diaphragm is larger than that of the drive cone, inner and outer diameter of the one edge unit is larger than that of the other edge unit.
The magnetic circuit unit includes a permanent magnet, and the voice coil is disposed in a magnetic gap of the magnetic circuit.
In the speaker having the above described configuration, by supplying voice currents to the voice coil, electromagnetic force (Lorentz force) acts on the voice coil to vibrate the diaphragm and to generate sound corresponding to the voice currents in the sound emission direction.
Further, the speaker described above is a so-called air suspension speaker aiming for an improvement of reproduced sound quality and for a longer operating life by sealing a space surrounded by the drive cone, the diaphragm, the two edge units, and the frame.
[Patent Document 1] Japanese Published Patent Application No. 2005-191746